1. Field of the Invention
The present invention relates to a multiaxial double action oil hydraulic press having at least one upper press unit movable downwards and at least one lower press unit movable upwards, the press also having an upthrust lifting unit.
2. Description of the Prior Art
A double action oil hydraulic press having two pressing units made of an outer and an inner slide, respectively, has been known from JP 2001-105187.
The outer slide of this conventional double action oil hydraulic press is driven by an outer slide driving cylinder which is connected to a variable displacement oil hydraulic pump via an oil hydraulic circuit provided with a relief valve in its midway. The outer slide is actuated with the pressure oil from the variable displacement oil hydraulic pump, whose flow rate is controlled by an outer slide control unit.
The conventional double action oil hydraulic press is operable 3- or 5-axially with three or five pressing units each of which is operated by a single cylinder, and requires a large oil hydraulic reservoir. Typically, for example, a reservoir of 2000 liters in capacity is required for a 600 ton press, which inconveniently makes the entire press large-sized. Further inconveniences of the conventional press are that it is slow in pressing speed and thus low in productivity, and is also low in the accuracy with which the slide is brought to halt and which has so far been limited to 0.1 mm at best.